Ben,
Not quite what you wanted, I am sure, but I have done a few good cape holes with sand replacing water. For lost ball reasons, I often use sand for capes on the right side, reserving water for only the left, where I can. The 10th at Wild Wing in Myrtle Beach is one of my faves, with sand on the right, then 18 is a cape with water on the left.
Also OT, somewhat, but I learned early on that the angle of these cape holes ought not exceed 30 degrees in most cases. When working with Killian and Nugent, they did a lot of those, sometimes steeper. They just didn't think it through that hard until they hooked up with Jim Colbert. They took him to see a course then under construction, I think its called George Dunne now, a Forest Preserve Course SW of Chicago. He gets out of the cart, takes a look at the 45 degree angle, water left, bunkers framing behind, and says (in his normal colorful way....) "So, you are asking me to wear out a driver, and then stop it on a dime?" (Note, with new clubs it might be easier for him now....)
On the other side, any angle less than 10 degrees seems more like lateral water than a carry hazard, so 10-30 degrees works best on Cape Holes.
Like Pete Dye, I think a simple nearly straight edge works best. One, it makes the exact line harder to discern, two it avoids any potential for blind water that you might have if the shoreline randomly zigs and zags, hiding a perhaps critical portion of the water to the golfer deciding where to hit it.
Years ago, I was displaying at a golf show in Singapore, and the late Robin Nelson dragged one of his associates into my booth. He points to my rendering, which included a cape hole almost yelling, "See that?" Then, "Jeff, please tell him why that lake edge is so straight!" He and I laughed, but when you work in plan, and hire young landscape architects, they cannot seem to resist drawing the curvy lake edge (as taught in school....) and its a good lesson that not everything works on the ground as you think it might in plan, and the airplane view has little to do with quality golf.
Lastly, while I have put them where water or topo suggests, my preference is to locate such holes where they are normally downwind, which better entices players to take the chance. I have seen too many aim way wide when the wind is in the face, sort of reducing the fun factor of such a hole.